I finally got these done, felted and the non-skid applied. Love them!
I used the Fiber Trends Felted Clogs
pattern. The yarn on the red pair with the brown sole is Ella Rae Classic Solid held double. The yarn on the purple ones is Ella Rae Classic Solid held double on the sole and held with Manos del Uruguay Maxima for the upper.
We tried using rug backing (from Michaels) and it's white and rather hard to apply. I had put dots and two coats wasn't grippy. So I bought some Performix Super Grip
for fabric from Amazon and we applied 3 coats. It's clear and boy is it grippy!!! It's a little squeaky at first, but better than slipping which I'm prone to do.
Mine are the purple ones, DH's are the dark red with brown soles.